GScrollBar: Add the same hover highlight effect as GButton.

LibGUI/GScrollBar.cpp

@@ -197,14 +197,14 @@ void GScrollBar::paint_event(GPaintEvent& event)
 
     painter.fill_rect(rect(), Color::from_rgb(0xd6d2ce));
 
-    StylePainter::paint_button(painter, up_button_rect(), ButtonStyle::Normal, false);
+    StylePainter::paint_button(painter, up_button_rect(), ButtonStyle::Normal, false, m_hovered_component == Component::DecrementButton);
     painter.draw_bitmap(up_button_rect().location().translated(3, 3), orientation() == Orientation::Vertical ? *s_up_arrow_bitmap : *s_left_arrow_bitmap, has_scrubber() ? Color::Black : Color::MidGray);
 
-    StylePainter::paint_button(painter, down_button_rect(), ButtonStyle::Normal, false);
+    StylePainter::paint_button(painter, down_button_rect(), ButtonStyle::Normal, false, m_hovered_component == Component::IncrementButton);
     painter.draw_bitmap(down_button_rect().location().translated(3, 3), orientation() == Orientation::Vertical ? *s_down_arrow_bitmap : *s_right_arrow_bitmap, has_scrubber() ? Color::Black : Color::MidGray);
 
     if (has_scrubber())
-        StylePainter::paint_button(painter, scrubber_rect(), ButtonStyle::Normal, false);
+        StylePainter::paint_button(painter, scrubber_rect(), ButtonStyle::Normal, false, m_hovered_component == Component::Scrubber);
 }
 
 void GScrollBar::mousedown_event(GMouseEvent& event)
@@ -271,6 +271,19 @@ void GScrollBar::mouseup_event(GMouseEvent& event)
 
 void GScrollBar::mousemove_event(GMouseEvent& event)
 {
+    auto old_hovered_component = m_hovered_component;
+    if (scrubber_rect().contains(event.position()))
+        m_hovered_component = Component::Scrubber;
+    else if (up_button_rect().contains(event.position()))
+        m_hovered_component = Component::DecrementButton;
+    else if (down_button_rect().contains(event.position()))
+        m_hovered_component = Component::IncrementButton;
+    else if (rect().contains(event.position()))
+        m_hovered_component = Component::Gutter;
+    else
+        m_hovered_component = Component::Invalid;
+    if (old_hovered_component != m_hovered_component)
+        update();
     if (!m_scrubbing)
         return;
     float delta = orientation() == Orientation::Vertical ? (event.y() - m_scrub_origin.y()) : (event.x() - m_scrub_origin.x());
@@ -279,3 +292,8 @@ void GScrollBar::mousemove_event(GMouseEvent& event)
     float new_value = m_scrub_start_value + (value_steps_per_scrubbed_pixel * delta);
     set_value(new_value);
 }
+
+void GScrollBar::leave_event(GEvent&)
+{
+    m_hovered_component = Component::Invalid;
+}

LibGUI/GScrollBar.h

@@ -26,11 +26,20 @@ public:
 
     virtual const char* class_name() const override { return "GScrollBar"; }
 
+    enum Component {
+        Invalid,
+        DecrementButton,
+        IncrementButton,
+        Gutter,
+        Scrubber,
+    };
+
 private:
     virtual void paint_event(GPaintEvent&) override;
     virtual void mousedown_event(GMouseEvent&) override;
     virtual void mouseup_event(GMouseEvent&) override;
     virtual void mousemove_event(GMouseEvent&) override;
+    virtual void leave_event(GEvent&) override;
 
     int button_size() const { return orientation() == Orientation::Vertical ? width() : height(); }
     Rect up_button_rect() const;
@@ -52,4 +61,5 @@ private:
     Point m_scrub_origin;
 
     Orientation m_orientation { Orientation::Vertical };
+    Component m_hovered_component { Component::Invalid };
 };